The Panoramic View of Ecuadorian Soil Nutrients (Deficit/Toxicity) from Different Climatic Regions and Their Possible Influence on the Metabolism of Important Crops.

Soil nutrients influence all stages (reproduction, growth, and development) of a plant species' life, and it is known that the deficit and/or toxicity of one or more nutrients has negative effects on the production of crops of commercial interest. Ecuador represents one of the "mega-diverse" countries in the world, with an agricultural sector of great importance, due to its contribution to the country's economy. This review provides a panoramic view of soil nutrients from different climatic regions of Ecuador and revises the importance of knowledge about the possible influence of nutrients from the soil on the plant metabolism able to influence the crop resistance against pathogens or to enrich the biological characteristics of these crops.

Land-use change alters the bacterial community structure, but not forest management.

Deforestation has a large impact on soil fertility, especially on steep slopes, but by applying sustainable management practices, local communities in Oaxaca (Mexico) have tried to avoid the most negative effects on the forest ecosystems they manage. In this study, the characteristics and bacterial community structure were investigated from soil sampled in triplicate (n = 3) with different land use, i.e., arable, natural forest, sustainable managed, and reforested soil. The pH was significantly higher in the arable (6.2) than in the forest soils (≤ 5.3), while the organic matter was > 2 times higher in the natural forest (80.4 g/kg) and sustainable managed soil (86.3 g/kg) than in the arable (36.8 g/kg) and cleared and reforested soil (39.3 g/kg). The higher organic matter content in the first two soils was due to leaf litter, absent in the other soils. The species richness (q = 0), the typical (q = 1) and dominant bacteria (q = 2) were not affected significantly by land use. The beta diversity, however, showed a significant effect of land use on species richness (p = 0.0029). Proteobacteria (40.135%) and Actinobacteria (20.15%) were the dominant bacterial phyla, and Halomonas (14.50%) and the Verrucomicrobia DA101 (3.39%) were the dominant genera. The bacterial communities were highly significantly different in soil with different land use considering the taxonomic level of genus and OTUs (p ≤ 0.003). It was found that the sustainable managed forest provided the local community with sellable wood while maintaining the soil organic matter content, i.e., sequestered C and without altering the bacterial community structure.

Reducing Salinity by Flooding an Extremely Alkaline and Saline Soil Changes the Bacterial Community but Its Effect on the Archaeal Community Is Limited.

Regular flooding of the soil to reduce salinity will change soil characteristics, but also the microbial community structure. Soil of the former lake Texcoco with electrolytic conductivity (EC) 157.4 dS m-1 and pH 10.3 was flooded monthly in the laboratory under controlled conditions for 10 months while soil characteristics were determined and the archaeal and bacterial community structure monitored by means of 454 pyrosequencing of the 16S rRNA gene. The EC of the soil dropped from 157.8 to 1.7 dS m-1 and the clay content decreased from 430 to 270 g kg-1 after ten floodings, but the pH (10.3) did not change significantly over time. Flooding the soil had a limited effect on the archaeal community structure and only the relative abundance of Haloferax-like 16S rRNA phylotypes changed significantly. Differences in archaeal population structure were more defined by the initial physicochemical properties of the soil sample than by a reduction in salinity. Flooding, however, had a stronger effect on bacterial community structure than on the archaeal community structure. A wide range of bacterial taxa was affected significantly by changes in the soil characteristics, i.e., four phyla, nine classes, 17 orders, and 28 families. The most marked change occurred after only one flooding characterized by a sharp decrease in the relative abundance of bacterial groups belonging to the Gammaproteobacteria, e.g., Halomonadaceae (Oceanospirillales), Pseudomonadaceae, and Xanthomonadaceae and an increase in that of the [Rhodothermales] (Bacteroidetes), Nitriliruptorales (Actinobacteria), and unassigned Bacteria. It was found that flooding the soil sharply reduced the EC, but also the soil clay content. Flooding the soil had a limited effect on the archaeal community structure, but altered the bacterial community structure significantly.

Sewage sludges in physic nut seedlings macronutrient contents and chemical attributes of soil / Lodos de esgoto nos teores de macronutrientes em mudas de pinhão-manso e atributos químicos do solo

Ever since the government began providing incentives for biofuel production, physic nut has appeared to be a promising plant, due to the high oil content of the seeds. The purpose of this study was to evaluate the nutrition of physic nut seedlings and changes in the chemical attributes of soil, based on the doses of domestic and industrial sewage sludge. Two experiments were conducted in a design with casualized blocks with four replicates using samples of a "Latossolo Amarelo" that received five doses of each sludge, equivalent to 0; 100; 150; 200 and 300 kg N total ha-1. The domestic sewage sludge raised the calcium and magnesium contents in the dry mass of the aerial part and root, and nitrogen and phosphorus in the dry mass of the aerial part of physic nut seedlings, whereas the industrial sludge raised the calcium and nitrogen in the dry mass of the aerial part and root of the physic seedlings, but did not affect the phosphorus, nitrogen, magnesium and potassium contents in the dry mass of the aerial part and root. The domestic sludge did not alter the soil pH but raised the amounts of phosphorus, calcium + magnesium, cation exchange capacity, organic matter and reduced the exchangeable aluminum, while the industrial one raised the pH and the cation exchange capacity of the soil, increased the amounts of phosphorus, calcium + magnesium, and organic matter and reduced the exchangeable aluminum present in the soil. The domestic and industrial sludges may be used to produce physic nut seedlings; however is necessary studies to evaluate the presence of heavy metals or potentially pathogenic microorganisms.

Com os incentivos governamentais para produção de biocombustíveis, o pinhão-manso surgiu como uma planta promissora, devido ao alto teor de óleo nas sementes. Objetivou-se, com este estudo, avaliar a nutrição de mudas de pinhão-manso e alterações nos atributos químicos do solo, em função de doses de lodos de esgoto doméstico e industrial. Dois experimentos em um delineamento em blocos casualizados, com quatro repetições, foram conduzidos utilizando amostras de um Latossolo Amarelo que recebeu cinco doses de cada lodo, equivalentes a 0; 100; 150; 200 e 300 kg N total ha-1. O lodo de esgoto doméstico elevou os teores de cálcio e magnésio na massa seca da parte aérea e raiz e de nitrogênio e fósforo na massa seca da parte aérea das mudas de pinhão-manso, enquanto o lodo industrial elevou os teores de cálcio e nitrogênio na massa seca da parte aérea e raiz das mudas de pinhão-manso, porém não afetou os teores de fósforo, nitrogênio, magnésio e potássio na massa seca da parte aérea e raiz. O lodo doméstico não alterou o pH do solo, contudo elevou as quantidades de fósforo, cálcio + magnésio, a capacidade de troca catiônica, a matéria orgânica e reduziu o alumínio trocável, enquanto o industrial elevou o pH e a capacidade de troca catiônica do solo, aumentou as quantidades de fósforo, cálcio + magnésio e matéria orgânica e reduziu o alumínio trocável presentes no solo. Os lodos domésticos e industriais podem ser utilizados na produção de mudas de pinhão-manso, contudo é necessário estudos sobre a presença de metais pesados ou micro-organismos patogênicos.

Variation of arbuscular mycorrhizal fungal communities along an altitudinal gradient in rupestrian grasslands in Brazil.

Variation in arbuscular mycorrhizal fungi (AMF) communities is described for the first time in rupestrian grasslands in Brazil along an altitudinal gradient of 700 m (800 to 1400 m a.s.l.). Hypotheses tested were that soil properties influence the variation in AMF communities and that the frequency of the most common species of AMF is inversely influenced by the richness of other AMF. Field and laboratory data were collected on AMF community composition, richness, density, and frequency in the altitudinal gradient, and the relationships with several physical-chemical soil properties and altitude were evaluated. Fifty-one species of AMF were recorded, with 14 species being reported as possibly new to science and nine species representing new records for Brazil. This single elevation gradient alone contains 22% of the known world diversity of AMF. Soil properties and AMF community density and richness varied significantly along the elevation (p < 0.05). AMF density and richness were higher at the intermediate altitude, while AMF species composition differed statistically among the altitudes.